Variable displacement type compressor

ABSTRACT

A first swash plate  18  is coupled to a drive shaft  16  to be rotatable integrally with the drive shaft  16 . Single head pistons  23  are coupled to the first swash plate  18  via shoes  25 A,  25 B. Rotation of the drive shaft  16  rotates the first swash plate  18 , which causes the pistons  23  to reciprocate and compress refrigerant gas. The first swash plate  18  supports an annular second swash plate  51  to be rotatable relative to the first swash plate  18  via a ball bearing  52 . The second swash plate  51  is arranged between the first swash plate  18  and the shoes  25 B that receive a compressive load to be slidable with respect to the first swash plate  18  and the shoes  25 B. Inclined surfaces (chamfers) are provided on salient corners  18   b   , 18   c  of the first swash plate  18 . Therefore, the durability of the swash plates and the shoes are improved.

TECHNICAL FIELD

The present invention relates to a variable displacement swash platetype compressor that forms, for example, part of a refrigeration circuitand compresses refrigerant gas.

BACKGROUND ART

As shown in FIG. 9, such a swash plate type compressor includes a swashplate 92, which is coupled to a drive shaft 91 to be rotatableintegrally with the drive shaft 91. Single head pistons 94 are coupledto the outer circumferential portion of the swash plate 92 with pairs ofsemispherical shoes 93A, 93B. Therefore, when the swash plate 92 isrotated by rotation of the drive shaft 91, the swash plate 92 slideswith respect to the shoes 93A, 93B causing the pistons 94 toreciprocate, thereby compressing refrigerant gas.

Each pair of shoes 93A, 93B rotates about an axis S (a line that passesthrough the center of curvature P of the spherical surface and isperpendicular to sliding surfaces with respect to the swash plate 92) asthe shoes 93A, 93B rotate relative to the swash plate 92. The rotationof the shoes 93A, 93B about the axis S is caused because a rotationalforce is applied to the shoes 93A, 93B in one direction about the axis Sdue to the difference between the circumferential velocities of theinner and outer circumferences of the swash plate 92. More specifically,the circumferential velocity of the outer circumference of the swashplate 92 is greater than that of the inner circumference of the swashplate 92.

That is, the swash plate type compressor shown in FIG. 9 is configuredsuch that the shoes 93A, 93B directly slide against the swash plate 92.Therefore, the shoes 93A, 93B are unnecessarily rotated about the axis Sdue to the sliding motion caused as the shoes 93A, 93B rotate relativeto the swash plate 92. This increases the mechanical loss particularlyat the sliding portion between each piston 94 and the corresponding shoe93B that receives reactive force of compression, and causes problemssuch as seizure at the sliding portions.

To solve such problems, for example, a technique shown in FIG. 10 hasbeen proposed (for example, patent document 1). That is, an annular step90 a is provided at the center of a rear surface (a surface facingrightward in FIG. 10) of a swash plate (hereinafter, referred to as afirst swash plate 90). An annular sliding plate (hereinafter, referredto as a second swash plate 95) is arranged outward of the step 90 a ofthe first swash plate 90. The second swash plate 95 is supported to becoaxial with and rotatable relative to the first swash plate 90. Theouter circumferential portion of the second swash plate 95 is arrangedbetween the first swash plate 90 and the second shoes 93B to be slidablewith respect to the first swash plate 90 and the second shoes 93B.

Therefore, when the first swash plate 90 is rotated, the first swashplate 90 slides relative to the second swash plate 95, which reduces therotation speed of the second swash plate 95 as compared to the rotationspeed of the first swash plate 90. This reduces the relative rotationspeed of the second swash plate 95 and the second shoes 93B as comparedto the relative rotation speed of the second shoes 93B and the firstswash plate 90. As a result, the rotation of each second shoe 93B aboutthe axis S caused by the relative rotation of the second swash plate 95and the second shoes 93B is suppressed, which suppresses mechanical lossand occurrence of problems.

A configuration has also been proposed in which rolling elements areprovided between the first shoes 93A and the second shoes 93B andbetween the first swash plate 90 and the second swash plate 95 (forexample, patent document 2). In the patent document 2, a race of athrust bearing arranged toward the second shoe 93B can be considered asthe second swash plate 95. With this configuration, the first swashplate 90 reliably slides with respect to the second swash plate 95,which significantly reduces the relative rotation speed of the secondswash plate 95 and the second shoes 93B as compared to the relativerotation speed of the second shoes 93B and the first swash plate 90.

However, according to the swash plate configuration including the secondswash plate 95 and the rolling element in addition to the first swashplate 90, the thickness between the first shoes 93A and the second shoes93B is increased. The first swash plate 90, which tilts with respect tothe drive shaft 91, has a salient corner 90 b at the outercircumferential edge portion corresponding to the vicinity of the piston94 located at the top dead center position (the state shown in FIG. 10).The salient corner 90 b is provided at the outer circumferential edgeportion opposite to the second swash plate 95 and significantlyprotrudes in the radial direction (upward in the drawing) of the driveshaft 91. Furthermore, the second swash plate 95, which tilts withrespect to the drive shaft 91, has a salient corner 95 b at the outercircumferential edge portion corresponding to the vicinity of the piston94 located at the bottom dead center position (not shown). The salientcorner 95 b is provided at the outer circumferential edge portionopposite to the first swash plate 90 and significantly protrudes in theradial direction of the drive shaft 91.

When the salient corner 90 b of the first swash plate 90 and the salientcorner 95 b of the second swash plate 95 significantly protrude in theradial direction of the drive shaft 91, part of each piston 94corresponding to the protruding portions needs to be made thin, or thepistons 94 need to be enlarged in the radial direction to avoidinterference with the protruding portions. Reducing the thickness of thepistons 94 leads to reduction in the durability, and enlargement of thepistons 94 leads to enlargement of the swash plate type compressor.Therefore, in the prior art, when the thickness of the swash plateconfiguration needs to be increased, the radii of the first swash plate90 and the second swash plate 95 are reduced to avoid interference ofthe salient corners 90 b, 95 b with the pistons 94.

However, when the radii of the first swash plate 90 and the second swashplate 95 are reduced, particularly the piston 94 located in the vicinityof the top dead center position (in a compression stroke) has a reducedcontact area between the second shoe 93B, which receives a significantreaction force of compression, and the second swash plate 95. Thisundesirably reduces the durability of the second swash plate 95 and thesecond shoe 93B.

It has become a common practice to use carbon dioxide as refrigerant ofthe refrigeration circuit. When carbon dioxide refrigerant is used, thepressure in the refrigeration circuit becomes extremely high as comparedto a case where chlorofluorocarbon refrigerant (for example, R134a) isused. Therefore, the reaction force of compression applied to thepistons 94 is increased in the swash plate type compressor, and theaforementioned problem (reduction in the durability of the second swashplate 95 and the second shoes 93B) has become a significant matter ofconcern.

Patent Document 1: Japanese Laid-Open Patent Publication No. 8-338363(page 4, FIG. 1)

Patent Document 2: Japanese Laid-Open Patent Publication No. 8-28447(page 3, FIG. 1)

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide avariable displacement swash plate type compressor that improves thedurability of a swash plate and shoes while suppressing reduction in thedurability of pistons and enlargement of the pistons.

To achieve the above objective, the present invention provides avariable displacement swash plate type compressor. A swash plate iscoupled to a drive shaft to be rotatable integrally with the driveshaft. Pistons are coupled to the swash plate via shoes. Rotation of thedrive shaft rotates the swash plate, which causes the pistons toreciprocate and compress gas. The displacement is changed by varying theinclination angle of the swash plate. An inclined surface is provided atpart of the entire outer circumferential edge portion of the swashplate.

Providing the inclined surface at a projecting salient corner of theouter circumferential edge portion of the swash plate, which inclineswith respect to the drive shaft, permits the diameter of the swash plateto be increased while suppressing decrease of the durability andenlargement of the pistons. Therefore, a significant reaction force ofcompression applied to the swash plate via the shoes is received in asuitable manner. This improves the durability of the swash plate and theshoes.

In a preferred embodiment, part of the outer circumferential edgeportion of the swash plate corresponding to the piston located at thetop dead center position is provided with the inclined surface on asalient corner opposite to the piston. That is, part of the outercircumferential edge portion of the swash plate corresponding to acircumferential range of the swash plate that arranges any of thepistons at the top dead center position is provided with the inclinedsurface on the salient corner opposite to the piston.

At the outer circumferential edge portion of the swash plate thatcorresponds to the piston located at the top dead center position, thesalient corner opposite to the piston significantly projects in theradial direction of the drive shaft when the swash plate tilts withrespect to the drive shaft. Therefore, a significant reaction force ofcompression applied to the swash plate via the shoe of the pistonlocated in the vicinity of the top dead center position is received in asuitable manner. This improves the durability of the swash plate and theshoes.

In a preferred embodiment, part of the outer circumferential edgeportion of the swash plate corresponding to the piston located at thebottom dead center position is provided with the inclined surface on asalient corner toward the piston. That is, part of the outercircumferential edge portion of the swash plate corresponding to acircumferential range of the swash plate that arranges any of thepistons at the bottom dead center position is provided with the inclinedsurface on the salient corner toward the piston.

At the outer circumferential edge portion of the swash platecorresponding to the piston located at the bottom dead center position,the salient corner toward the piston significantly projects in theradial direction of the drive shaft. Therefore, chamfering theprojecting portion of the swash plate permits the diameter of the firstswash plate to be increased while suppressing decrease of the durabilityand enlargement of the pistons.

In the preferred embodiment, the swash plate includes a first swashplate, which is coupled to the drive shaft to be rotatable integrallywith the drive shaft, and a second swash plate, which is supported bythe first swash plate. The pistons are coupled to the first and secondswash plates via first shoes, which abut against the first swash plate,and second shoes, which abut against the second swash plate and receivea reaction force of compression. Part of the outer circumferential edgeof the first swash plate corresponding to the piston located at the topdead center position is provided with the inclined surface on a salientcorner opposite to the second swash plate. That is, part of the outercircumferential edge portion of the first swash plate corresponding to acircumferential range of the first swash plate that arranges any of thepistons at the top dead center position is provided with the inclinedsurface on the salient corner opposite to the first swash plate.

At the outer circumferential edge portion of the first swash plate thatcorresponds to the piston located at the top dead center position, thesalient corner opposite to the second swash plate significantly projectsin the radial direction of the drive shaft when the first swash platetilts with respect to the drive shaft. Therefore, chamfering theprojecting portion of the first swash plate permits the diameter of thefirst swash plate to be increased while suppressing decrease of thedurability and enlargement of the pistons. Therefore, the first swashplate supports the second swash plate in a suitable manner, and a greatreaction force of compression applied to the second swash plate via thesecond shoe of the piston located in the vicinity of the top dead centerposition is received by the first swash plate via the second swash platein a suitable manner. This improves the durability of the second swashplate and the second shoes.

In the preferred embodiment, part of the outer circumferential edgeportion of the first swash plate corresponding to the piston located atthe bottom dead center position is provided with the inclined surface ona salient corner toward the second swash plate. That is, part of theouter circumferential edge portion of the first swash platecorresponding to a circumferential range of the first swash plate thatarranges any of the pistons at the bottom dead center position isprovided with the inclined surface on the salient corner toward thesecond swash plate.

At the outer circumferential edge portion of the swash platecorresponding to the piston located at the bottom dead center position,the salient corner toward the piston significantly projects in theradial direction of the drive shaft. Therefore, chamfering theprojecting portion of the swash plate permits the diameter of the firstswash plate to be increased while suppressing decrease of the durabilityand enlargement of the pistons.

In the preferred embodiment, the gas is refrigerant used in arefrigeration circuit, and carbon dioxide is used as the refrigerant.

When carbon dioxide refrigerant is used, as compared to a case wherechlorofluorocarbon refrigerant (for example, R134a) is used, thepressure in the refrigeration circuit becomes extremely high. Therefore,the reaction force of compression applied to the pistons in the variabledisplacement swash plate type compressor is increased, which increasesthe pressure between the swash plate and the shoes. The above mentionedembodiments of the present invention according to any one of claims 1 to5 are particularly effective in improving the durability of the swashplate and the shoes while suppressing decrease of the durability andenlargement of the pistons.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view illustrating a variabledisplacement swash plate type compressor according to a first embodimentof the present invention;

FIG. 2 is an enlarged partial view of FIG. 1 with the first and secondswash plates not being sectioned;

FIG. 3 is a longitudinal cross-sectional view illustrating a variabledisplacement swash plate type compressor according to a secondembodiment of the present invention;

FIG. 4 is an enlarged partial view of FIG. 3 with the first and secondswash plates not being sectioned (partially cut away) and part of thefirst and second shoes being sectioned;

FIG. 5 is an enlarged partial view illustrating a swash plateconfiguration according to a third embodiment of the present invention;

FIG. 6 is a longitudinal cross-sectional view illustrating a variabledisplacement swash plate type compressor according to a fourthembodiment of the present invention;

FIG. 7 is a cross-sectional view taken along line A-A of FIG. 6;

FIG. 8 is an enlarged partial cross-sectional view of FIG. 6;

FIG. 9 is a longitudinal cross-sectional view illustrating a prior artvariable displacement swash plate type compressor; and

FIG. 10 is a partial cross-sectional view illustrating a prior arttechnique.

BEST MODE FOR CARRYING OUT THE INVENTION

A variable displacement swash plate type compressor according to firstto fourth embodiments of the present invention will now be described.The compressor forms part of a refrigeration circuit of a vehicleair-conditioning system.

The first embodiment will be described with reference to FIGS. 1 and 2.

FIG. 1 is a longitudinal cross-sectional view of the variabledisplacement swash plate type compressor (hereinafter, simply referredto as the compressor) 10. The left end of the compressor 10 in FIG. 1 isdefined as the front of the compressor 10, and the right end is definedas the rear of the compressor 10.

As shown in FIG. 1, a housing of the compressor 10 includes a cylinderblock 11, a front housing member 12 secured to the front end of thecylinder block 11, and a rear housing member 14 secured to the rear endof the cylinder block 11 with a valve plate assembly 13 in between.

In the housing of the compressor 10, the cylinder block 11 and the fronthousing member 12 define a crank chamber 15. A drive shaft 16 isrotatably arranged between the cylinder block 11 and the front housingmember 12 and extends through the crank chamber 15. The drive shaft 16is coupled to a power source of the vehicle, which is an engine E inthis embodiment, through a clutchless type power transmission mechanismPT, which constantly transmits power. Therefore, the drive shaft 16 isalways rotated by the power supply from the engine E when the engine Eis running.

A rotor 17 is coupled to the drive shaft 16 and is located in the crankchamber 15. The rotor 17 rotates integrally with the drive shaft 16. Thecrank chamber 15 accommodates a substantially disk-like first swashplate 18. A through hole 18 a is formed at the center of the first swashplate 18. The drive shaft 16 is inserted through the through hole 18 aof the first swash plate 18. The first swash plate 18 is supported bythe drive shaft 16 via the through hole 18 a to be slidable and tiltablewith respect to the drive shaft 16. A hinge mechanism 19 is locatedbetween the rotor 17 and the first swash plate 18.

The hinge mechanism 19 includes two rotor protrusions 41 (one of theprotrusions 41 located toward the front of the sheet of FIG. 1 is notshown), which protrude from the rear surface of the rotor 17, and aswash plate protrusion 42, which protrudes from the front surface of thefirst swash plate 18 toward the rotor 17. The distal end of the swashplate protrusion 42 is inserted between the two rotor protrusions 41.Therefore, rotational force of the rotor 17 is transmitted to the firstswash plate 18 via the rotor protrusions 41 and the swash plateprotrusion 42.

A substantially cylindrical support portion 39 projects at the center ofthe rear surface of the first swash plate 18 to surround the drive shaft16. A disk-like second swash plate 51 is arranged outward of the supportportion 39 of the first swash plate 18. A support hole 51 a is formed atthe center of the second swash plate 51. The support portion 39 isinserted in the support hole 51 a. The radius of the second swash plate51 is substantially the same as that of the first swash plate 18.

A radial bearing 52 is provided between the outer circumferentialsurface of the support portion 39 and the inner circumferential surfaceof the support hole 51 a of the second swash plate 51. A thrust bearing53 is provided between the rear surface of the first swash plate 18 andthe front surface of the second swash plate 51. The thrust bearing 53has rolling elements, which are rollers 53 a in this embodiment, and therollers 53 a are rotatably held by a retainer 53 b.

The second swash plate 51 is supported by the first swash plate 18 (thesupport portion 39) via the radial bearing 52 and the thrust bearing 53such that the second swash plate 51 rotates relative to and tiltintegrally with the first swash plate 18.

A cam portion 43 is formed at the proximal end of the rotor protrusions41. A cam surface 43 a is formed on the rear end face of the cam portion43 facing the first swash plate 18. The distal end of the swash plateprotrusion 42 slidably abuts against the cam surface 43 a of the camportion 43. Therefore, the hinge mechanism 19 guides the inclination ofthe first swash plate 18 and the second swash plate 51 as the distal endof the swash plate protrusion 42 moves toward and apart from the driveshaft 16 along the cam surface 43 a of the cam portion 43.

Cylinder bores 22 are formed in the cylinder block 11 about the axis Lof the drive shaft 16 at equal angular intervals and extend in thefront-rear direction (left-right direction on the sheet of FIG. 1). Asingle head piston 23 is accommodated in each cylinder bore 22 to bemovable in the front-rear direction. The front and rear openings of eachcylinder bore 22 are closed by the front end face of the valve plateassembly 13 and the associated piston 23. Each cylinder bore 22 definesa compression chamber 24. The volume of each compression chamber 24changes according to the reciprocation of the corresponding piston 23.

Each piston 23 is formed by coupling, in the front-rear direction, acolumnar head portion 37, which is inserted in the associated cylinderbore 22, and a neck 38 located in the crank chamber 15 outside thecylinder bore 22. The head portions 37 and the necks 38 are formed of analuminum based metal material (pure aluminum or an aluminum alloy). Apair of shoe seats 38 a are formed in each neck 38. Each neck 38accommodates semispherical first and second shoes 25A, 25B. The firstshoe 25A and the second shoe 25B are formed of iron based metalmaterial. In this specification, “semisphere” refers not only to a halfof a sphere, but also to a shape that includes part of a sphericalsurface of a sphere.

The first shoe 25A and the second shoe 25B are each received by thecorresponding shoe seat 38 a via a semispherical surface 25 a. Thesemispherical surface 25 a of the first shoe 25A and the semisphericalsurface 25 a of the second shoe 25B are located on the same sphericalsurface defined about a point P. Each piston 23 is coupled to the outercircumferential portion of the first swash plate 18 and the second swashplate 51 via the first shoe 25A and the second shoe 25B. The first shoe25A located opposite to the compression chamber 24 abuts against thefront surface of the first swash plate 18 via a planar sliding surface25 b provided opposite to the semispherical surface 25 a. The secondshoe 25B located toward the compression chamber 24, that is, the onethat receives reaction force of compression abuts against the rearsurface of the second swash plate 51 via a sliding surface 25 b providedopposite to the semispherical surface 25 a.

When the first swash plate 18 is rotated by the rotation of the driveshaft 16, the pistons 23 reciprocate in the front-rear direction.

When the first swash plate 18 is rotated, the radial bearing 52 and thethrust bearing 53 cause the first swash plate 18 to slide with respectto the second swash plate 51. This reduces the rotation speed of thesecond swash plate 51 as compared to the rotation speed of the firstswash plate 18. Therefore, the relative rotation speed of the secondswash plate 51 and the second shoes 25B is reduced as compared to therelative rotation speed of the second shoes 25B and the first swashplate 18. This suppresses the rotation of each second shoe 25B about theaxis S (a line that passes through the center of curvature point P ofthe semispherical surface 25 a and is perpendicular to the slidingsurface 25 b) caused by the relative rotation of the second swash plate51 and the second shoe 25B. Thus, mechanical loss and occurrence ofproblems caused by the rotation of the second shoes 25B are suppressed.

An intake chamber 26 and a discharge chamber 27 are defined between thevalve plate assembly 13 and the rear housing member 14 in the housing ofthe compressor 10. The valve plate assembly 13 includes intake ports 28and intake valves 29 located between the compression chambers 24 and theintake chamber 26. The valve plate assembly 13 also includes dischargeports 30 and discharge valves 31 located between the compressionchambers 24 and the discharge chamber 27.

As refrigerant of the refrigeration circuit, carbon dioxide is used.Refrigerant gas introduced into the intake chamber 26 from an externalcircuit, which is not shown, is drawn into each compression chamber 24via the associated intake port 28 and the intake valve 29 as thecorresponding piston 23 moves from the top dead center position to thebottom dead center position. The refrigerant gas that is drawn into thecompression chamber 24 is compressed to a predetermined pressure as thepiston 23 is moved from the bottom dead center position to the top deadcenter position, and is discharged to the discharge chamber 27 throughthe associated discharge port 30 and the discharge valve 31. Therefrigerant gas in the discharge chamber 27 is then conducted to theexternal circuit.

A bleed passage 32, a supply passage 33, and a control valve 34 areprovided in the housing of the compressor 10. The bleed passage 32connects the crank chamber 15 to the intake chamber 26. The supplypassage 33 connects the discharge chamber 27 to the crank chamber 15.The control valve 34, which is a conventional electromagnetic valve, islocated in the supply passage 33.

The opening degree of the control valve 34 is adjusted by controllingpower supply from the outside to control the balance between the flowrate of highly pressurized discharge gas supplied to the crank chamber15 through the supply passage 33 and the flow rate of gas conducted outof the crank chamber 15 through the bleed passage 32. The pressure inthe crank chamber 15 is thus determined. As the pressure in the crankchamber 15 varies, the difference between the pressure in the crankchamber 15 and the pressure in the compression chamber 24 is changed,which in turn varies the inclination angle of the first swash plate 18and the second swash plate 51. Accordingly, the stroke of each piston23, or the compressor displacement is adjusted.

For example, when the opening degree of the control valve 34 is reduced,the pressure in the crank chamber 15 is reduced. Therefore, theinclination angle of the first swash plate 18 and the second swash plate51 increases, thereby increasing the stroke of each piston 23. Thus, thedisplacement of the compressor 10 is increased. In contrast, when theopening degree of the control valve 34 increases, the pressure in thecrank chamber 15 is increased. Therefore, the inclination angle of thefirst swash plate 18 and the second swash plate 51 is reduced, therebyreducing the stroke of each piston 23. Thus, the displacement of thecompressor 10 is reduced.

As shown in FIGS. 1 and 2, the support portion 39 of the first swashplate 18 supporting the second swash plate 51 is provided at a positiondecentered from the axis M1 of the first swash plate 18 toward thepiston 23A located at the top dead center position. In other words, thesupport portion 39 is provided at a position decentered toward a sectionof the first swash plate (toward the hinge mechanism 19) that causes anyof the pistons 23 to be located at the top dead center position asviewed in the radial direction of the first swash plate 18 from the axisM1. Therefore, the second swash plate 51, the radial bearing 52, and thethrust bearing 53 (and the retainer 53 b) are decentered from the firstswash plate 18 toward the piston 23A located at the top dead centerposition. Therefore, the axis M2 of the second swash plate 51, theradial bearing 52, and the thrust bearing 53 is slightly displaced inparallel from the axis M1 of the first swash plate 18 toward the centerpoint P of the first shoe 25A and the second shoe 25B of the piston 23Alocated at the top dead center position (for example, 0.05 to 5 mm,although the displacement is exaggerated in FIGS. 1 and 2).

Therefore, part of the outer circumferential edge portion of the secondswash plate 51 corresponding to the vicinity of the piston 23A locatedat the top dead center position slightly protrudes in the radialdirection of the first swash plate 18 from the outer circumferentialedge portion of the first swash plate 18. Therefore, for example, ascompared to a case where the second swash plate 51 is not decenteredfrom the first swash plate 18, the contact area between the second shoe25B of the piston 23 located in the vicinity of the top dead centerposition and the second swash plate 51 is increased.

Part of the outer circumferential edge portion of the second swash plate51 corresponding to the vicinity of the piston 23B located at the bottomdead center position is located radially inward of the first swash plate18 from the outer circumferential edge portion of the first swash plate18. That is, part of the outer circumferential edge portion of thesecond swash plate 51 corresponding to the vicinity of the hingemechanism 19 is located radially inward of the first swash plate 18 thanthe outer circumferential edge portion of the first swash plate 18.Therefore, for example, as compared to a case where the second swashplate 51 is not decentered from the first swash plate 18, the contactarea between the second shoe 25B of the piston 23 located in thevicinity of the bottom dead center position and the second swash plate51 is reduced. However, the reaction force of compression applied to thesecond shoe 25B of the piston 23 located in the vicinity of the bottomdead center position is far smaller than the reaction force ofcompression applied to the second shoe 25B of the piston 23 located inthe vicinity of the top dead center position. Therefore, even if thecontact area between the second shoe 25B of the piston 23 located in thevicinity of the bottom dead center position and the second swash plate51 is reduced, no problem arises in the durability of the second swashplate 51 and the second shoe 25B.

Part of the outer circumferential edge portion of the first swash plate18 corresponding to the piston 23A located at the top dead centerposition and circumferentially adjacent parts thereof are provided withan inclined surface (a chamfer) on a salient corner 18 b opposite to thesecond swash plate 51. That is, part of the outer circumferential edgeportion of the second swash plate 51 corresponding to the vicinity ofthe hinge mechanism 19 is provided with the inclined surface (thechamfer) on the salient corner 18 b opposite to the second swash plate51. In other words, part of the outer circumferential edge portion ofthe first swash plate 18 corresponding to a circumferential range of thefirst swash plate 18 that arranges any of the pistons 23 at the top deadcenter position is provided with the inclined surface on the salientcorner 18 b opposite to the piston 23A. The inclined surface (thechamfer) on the salient corner 18 b is the largest at the partcorresponding to the piston 23A located at the top dead center position,and gradually becomes smaller along the circumferential direction. Theinclined surface (the chamfer) on the salient corner 18 b is providedwithin a range of quarter to half the circumference of the first swashplate 18 with the part corresponding to the piston 23A located at thetop dead center position arranged in the middle.

Part of the outer circumferential edge portion of the first swash plate18 corresponding to the piston 23B located at the bottom dead centerposition and circumferentially adjacent parts thereof are provided withan inclined surface (a chamfer) on a salient corner 18 c toward thesecond swash plate 51. That is, part of the outer circumferential edgeportion of the first swash plate 18 corresponding to a circumferentialrange of the first swash plate 18 that arranges the piston 23B at thebottom dead center position is provided with the inclined surface on thesalient corner 18 c opposite to the piston 23B.

The inclined surface (the chamfer) is the largest at the partcorresponding to the piston 23B located at the bottom dead centerposition, and gradually becomes smaller along the circumferentialdirection. The inclined surface (the chamfer) of the salient corner 18 cis provided within a range of quarter to half the circumference of thefirst swash plate 18 with the part corresponding to the piston 23Blocated at the bottom dead center position arranged in the middle. Theinclined surface (the chamfer) on the salient corner 18 c issubstantially the same size as the inclined surface (the chamfer) on thesalient corner 18 b taking into consideration of the balance of theweight around the axis M1 of the first swash plate 18.

The first embodiment has the following advantages.

(1-1) The second swash plate 51 is decentered from the first swash plate18 toward the piston 23A located at the top dead center position.Therefore, the contact area between the second shoe 25B of the piston 23located in the vicinity of the top dead center position and the secondswash plate 51 is increased without increasing the diameter of the firstswash plate 18 and the second swash plate 51. Therefore, the secondswash plate 51 reliably slides with respect to the second shoes 25B, andthe durability of the second swash plate 51 and the second shoes 25B isimproved while suppressing decrease of the durability and enlargement ofthe pistons 23.

(1-2) According to the swash plate configuration that includes thethrust bearing 53 in addition to the first swash plate 18 and the secondswash plate 51 as in the first embodiment, the thickness of the swashplate configuration between the first shoes 25A and the second shoes 25Bis increased. In such a configuration with a severe condition,decentering the second swash plate 51 with respect to the first swashplate 18 to increase the contact area between the second shoe 25B of thepiston 23 located in the vicinity of the top dead center position andthe second swash plate 51 is particularly effective in improving thedurability of the second swash plate 51 and the second shoes 25B whilesuppressing decrease of the durability and the enlargement of thepistons 23.

(1-3) Part of the outer circumferential edge portion of the first swashplate 18 corresponding to the piston 23A located at the top dead centerposition is provided with the inclined surface on the salient corner 18b opposite to the second swash plate 51. Also, part of the outercircumferential edge portion of the first swash plate 18 correspondingto the piston 23B located at the bottom dead center position is providedwith the inclined surface on the salient corner 18 c toward the secondswash plate 51. At the outer circumferential edge portion of the firstswash plate 18 that corresponds to the piston 23A located at the topdead center position, the salient corner 18 b opposite to the secondswash plate 51 significantly projects in the radial direction of thedrive shaft 16 when the first swash plate 18 tilts with respect to thedrive shaft 16. Also, at the outer circumferential edge portion of thefirst swash plate 18 corresponding to the piston 23B located at thebottom dead center position, the salient corner 18 c toward the secondswash plate 51 significantly projects in the radial direction of thedrive shaft 16.

Therefore, providing the inclined surfaces at the projecting portions ofthe first swash plate 18 (part of the entire circumference of thesalient corners 18 b, 18 c) permits the diameter of the first swashplate 18 to be increased while suppressing decrease of the durabilityand enlargement of the pistons 23. Therefore, the first swash plate 18supports the second swash plate 51 in a suitable manner, and a greatreaction force of compression applied to the second swash plate 51 viathe second shoe 25B of the piston 23 located in the vicinity of the topdead center position is received by the first swash plate 18 via thesecond swash plate 51 in a suitable manner. This improves the durabilityof the second swash plate 51.

(1-4) As the refrigerant of the refrigeration circuit, carbon dioxide isused. When carbon dioxide refrigerant is used, the pressure in therefrigeration circuit becomes extremely high as compared to a case wherechlorofluorocarbon refrigerant (for example, R134a) is used. Therefore,the reaction force of compression applied to the pistons 23 in thecompressor is increased, which increases the pressure between the secondswash plate 51 and the second shoes 25B. The first embodiment of thepresent invention is thus particularly effective in improving thedurability of the second swash plate 51 and the second shoes 25B whilesuppressing decrease of the durability and enlargement of the pistons23.

Next, a second embodiment of the present invention will be describedwith reference to FIGS. 3 and 4. In the second embodiment, onlydifferences from the first embodiment are explained. Like or the samemembers are given the like or the same numbers and detailed explanationsare omitted.

As for the first shoes 25A and the second shoes 25B, each first shoe 25Alocated toward the hinge mechanism 19, or opposite to the associatedcompression chamber 24, slidably abuts against the front surface of anouter circumferential portion 18-1 of the first swash plate 18 via thesliding surface 25 b opposite to the semispherical surface 25 a. Also,each second shoe 25B located opposite to the hinge mechanism 19, ortoward the associated compression chamber 24, and receives the reactionforce of compression slidably abuts against the rear surface of an outercircumferential portion 51-2 of the second swash plate 51 via thesliding surface 25 b opposite to the semispherical surface 25 a. Thecenter portion of the sliding surface 25 b of the first shoe 25A bulgestoward the first swash plate 18 (see FIG. 4. The bulge is exaggerated inFIG. 4). The sliding surface 25 b of the second shoe 25B is flat.

A radial bearing 52A, which is a roller bearing, is located between thesupport portion 39, which forms the inner circumferential portion of thefirst swash plate 18, and an inner circumferential portion 51-1 of thesecond swash plate 51, and more specifically, between the outercircumferential surface of the support portion 39 and the innercircumferential surface of the support hole 51 a of the second swashplate 51. The radial bearing 52A includes an outer race 52 a attached tothe inner circumferential surface of the support hole 51 a of the secondswash plate 51, an inner race 52 b attached to the outer circumferentialsurface of the support portion 39 of the first swash plate 18, androlling elements, which are rollers 52 c in the second embodiment. Therollers 52 c are located between the outer race 52 a and the inner race52 b.

The thrust bearing 53, which is a roller bearing, is located between thefirst shoes 25A and the second shoes 25B and between the outercircumferential portion 18-1 of the first swash plate 18 and the outercircumferential portion 51-2 of the second swash plate 51. The thrustbearing 53 has rolling elements, which are the rollers 53 a in thesecond embodiment, and the rollers 53 a are rotatably held by theretainer 53 b. The thrust bearing 53 has an annular race 55 locatedbetween the rollers 53 a and the first swash plate 18. The race 55 isformed by carburizing and heat treating base material formed of mildsteel such as SPC. The corners at both ends of each roller 53 a arechamfered to prevent the second swash plate 51 and the race 55 frombeing damaged by the rollers 53 a abutting against the second swashplate 51 and the race 55.

An annular engaging portion 18 d is provided on the rear surface of thefirst swash plate 18 at the outermost circumference of the outercircumferential portion 18-1 and projects toward the second swash plate51. The race 55 is located inward of the engaging portion 18 d and isengaged with the first swash plate 18 at the radially outward edge ofthe race 55 by the abutment between the outer circumferential edge ofthe race 55 and the engaging portion 18 d. The race 55 is guided by theengaging portion 18 d to rotate relative to the first swash plate 18.

The second swash plate 51 is supported by the first swash plate 18 viathe radial bearing 52A and the thrust bearing 53 such that the secondswash plate 51 rotates relative to and tilts integrally with the firstswash plate 18. Therefore, when the first swash plate 18 is rotated, theradial bearing 52A and the thrust bearing 53 cause rolling motionbetween the first swash plate 18 and the second swash plate 51.Therefore, the mechanical loss caused by sliding motion between thefirst swash plate 18 and the second swash plate 51 is converted to themechanical loss caused by the rolling motion. This significantlysuppresses the mechanical loss in the compressor.

The plate thickness Y1 of the inner circumferential portion 51-1 of thesecond swash plate 51 that is supported by the radial bearing 52A isgreater than the plate thickness Y2 of the outer circumferential portion51-2 of the second swash plate 51 that is supported by the thrustbearing 53. More specifically, the plate thickness Y2 of the outercircumferential portion 51-2 of the second swash plate 51 is half ormore of the plate thickness X of the outer circumferential portion 18-1of the first swash plate 18 and thinner than the plate thickness X ofthe outer circumferential portion 18-1 of the first swash plate 18.Also, the plate thickness Y1 of the inner circumferential portion 51-1of the second swash plate 51 is thicker than the plate thickness X ofthe outer circumferential portion 18-1 of the first swash plate 18.

The plate thickness of the inner circumferential portion 51-1 of thesecond swash plate 51 is designed to be greater than that of the outercircumferential portion 51-2 of the second swash plate 51 (Y1>Y2) byproviding a cylindrical first projection 56, which projects toward thefirst swash plate 18, and a cylindrical second projection 57, whichprojects opposite to the first swash plate 18. The first projection 56and the second projection 57 are arranged coaxial with the support hole51 a, and the inner circumferential surfaces of the first projection 56and the second projection 57 form part of the inner circumferentialsurface of the support hole 51 a. The outer diameter Z2 of the secondprojection 57 is smaller than the outer diameter Z1 of the firstprojection 56. Also, the outer circumferential corner 57 a of the distalend face of the second projection 57 is entirely chamfered to form atapered face.

The second embodiment provides the following advantages in addition tothe advantages of the first embodiment.

(2-1) The thrust bearing 53, which supports the second swash plate 51 tobe rotatable relative to the first swash plate 18, is arranged betweenthe first shoes 25A and the second shoes 25B and between the outercircumferential portion 18-1 of the first swash plate 18 and the outercircumferential portion 51-2 of the second swash plate 51. The radialbearing 52A, which supports the second swash plate 51 to be rotatablerelative to the first swash plate 18, is arranged between the innercircumferential portion (the support portion 39) of the first swashplate 18 and the inner circumferential portion 51-1 of the second swashplate 51.

Therefore, the thrust bearing 53 and the radial bearing 52A effectivelyreduce the rotational resistance caused between the outercircumferential portion 18-1 of the first swash plate 18 and the outercircumferential portion 51-2 of the second swash plate 51, and betweenthe inner circumferential portion (the support portion 39) of the firstswash plate 18 and the inner circumferential portion 51-1 of the secondswash plate 51. Therefore, even in the compressor 10 used for therefrigeration circuit that uses carbon dioxide as refrigerant, thesliding motion between the first swash plate 18 and the second swashplate 51 is converted to the mechanical loss caused by the rollingmotion. As a result, problems such as the mechanical loss and theseizure are effectively suppressed.

(2-2) The plate thickness Y2 of the outer circumferential portion 51-2of the second swash plate 51 is half or more of the plate thickness X ofthe outer circumferential portion 18-1 of the first swash plate 18 andthinner than the plate thickness X of the outer circumferential portion18-1. To avoid enlargement of the pistons 23, that is, enlargement ofthe compressor, a space between the first shoes 25A and the second shoes25B is limited. In this limited space, when the plate thickness X of theouter circumferential portion 18-1 of the first swash plate 18 isincreased, the plate thickness Y2 of the outer circumferential portion51-2 of the second swash plate 51 needs to be reduced. In contrast, whenthe plate thickness Y2 of the outer circumferential portion 51-2 of thesecond swash plate 51 is increased, the plate thickness X of the outercircumferential portion 18-1 of the first swash plate 18 needs to bereduced.

In terms of receiving the reaction force of compression, the platethicknesses X, Y2 of the outer circumferential portions 18-1, 51-2 ofthe first swash plate 18 and the second swash plate 51 need to be asthick as possible to secure the strength. However, securing the platethickness X of the outer circumferential portion 18-1 of the first swashplate 18 to which power is transmitted from the drive shaft 16 shouldtake precedence to securing the plate thickness Y2 of the outercircumferential portion 51-2 of the second swash plate 51 that is onlyrequired to slide with respect to the first swash plate 18. In thisrespect, it is suitable to set the plate thickness Y2 of the outercircumferential portion 51-2 of the second swash plate 51 to be half ormore of the plate thickness X of the outer circumferential portion 18-1of the first swash plate 18 and thinner than the plate thickness X ofthe outer circumferential portion 18-1.

(2-3) In the second swash plate 51, the plate thickness Y1 of the innercircumferential portion 51-1 is greater than the plate thickness Y2 ofthe outer circumferential portion 51-2. The thick inner circumferentialportion 51-1 permits the second swash plate 51 to be stably supported bythe radial bearing 52A, and improves the sliding performance between thefirst swash plate 18 and the second swash plate 51. Furthermore, sincethe outer circumferential portion 51-2 of the second swash plate 51 isrelatively thinner than the inner circumferential portion 51-1, theplate thickness of the outer circumferential portion 18-1 of the firstswash plate 18 that is required to have a greater strength than thesecond swash plate 51 is easily secured.

(2-4) The plate thickness Y2 of the outer circumferential portion 51-2of the second swash plate 51 is thinner than the plate thickness X ofthe outer circumferential portion 18-1 of the first swash plate 18.Therefore, the thin outer circumferential portion 51-2 of the secondswash plate 51 facilitates securing the plate thickness of the outercircumferential portion 18-1 of the first swash plate 18 that isrequired to have a greater strength than the second swash plate 51. Theplate thickness Y1 of the inner circumferential portion 51-1 of thesecond swash plate 51 is greater than the plate thickness X of the outercircumferential portion 18-1 of the first swash plate 18. Therefore, theradial bearing 52A more stably supports the second swash plate 51.

(2-5) As for the first projection 56 and the second projection 57, whichform the inner circumferential portion 51-1 of the second swash plate51, the outer diameter Z2 of the second projection 57 is less than theouter diameter Z1 of the first projection 56. When the displacement ofthe compressor 10 is maximum (state shown in FIG. 3), for example, partof the second projection 57 significantly approaches the piston 23Blocated at the bottom dead center position. Therefore, it is effectiveto make the diameter of the second projection 57 to be smaller than thatof the first projection 56, thereby separating the second projection 57from the piston 23, in view of avoiding interference between the secondswash plate 51 and the pistons 23 while increasing the plate thicknessY1 of the inner circumferential portion 51-1 of the second swash plate51.

(2-6) As for the second projection 57, which forms the innercircumferential portion 51-1 of the second swash plate 51, the outercircumferential corner 57 a of the distal end face is chamfered. Whenthe displacement of the compressor is maximum, for example, part of theouter circumferential corner 57 a of the distal end face of the secondprojection 57 significantly approaches the piston 23B located at thebottom dead center position. Therefore, it is effective to provide thechamfer on the outer circumferential corner 57 a of the distal end faceof the second projection 57 in view of avoiding interference between thesecond swash plate 51 and the pistons 23 while increasing the platethickness Y1 of the inner circumferential portion 51-1 of the secondswash plate 51.

(2-7) Part of the outer circumferential edge of the first swash plate 18corresponding to the piston 23A located at the top dead center positionis provided with the inclined surface (the chamfer) on the salientcorner 18 b opposite to the second swash plate 51. Therefore, the firstswash plate 18 and the second swash plate 51 can be enlarged whilesuppressing reduction in the durability and enlargement of the pistons23. Therefore, the second swash plate 51 reliably slides with respect tothe second shoes 25B, and the durability of the second swash plate 51and the second shoes 25B is improved while suppressing reduction in thedurability and enlargement of the pistons 23.

That is, at the outer circumferential edge portion of the first swashplate 18 that corresponds to the piston 23A located at the top deadcenter position, the salient corner 18 b (that has not been chamfered)opposite to the second swash plate 51 significantly projects in theradial direction of the drive shaft 16 when the first swash plate 18tilts with respect to the drive shaft 16. When the salient corner 18 bof the first swash plate 18 opposite to the second swash plate 51significantly projects in the radial direction, the thickness of thenecks 38 of the pistons 23 need to be reduced corresponding to theprojecting portion, or the necks 38 need to be enlarged in the radialdirection to avoid interference with the projecting portion. However,reducing the thickness of the necks 38 leads to reduction in thedurability of the pistons 23, and enlargement of the necks 38 leads toenlargement of the compressor.

To solve such problems, the radius of the first swash plate 18 may bereduced to avoid interference between the salient corner 18 b and thepistons 23. However, when the radius of the first swash plate 18 isreduced, the radius of the second swash plate 51, which needs to besupported by the first swash plate 18, must also be reduced. Therefore,in particular, the contact area between the second swash plate 51 andthe second shoe 25B of the piston 23 located in the vicinity of the topdead center position (in the compression stroke) that receives asignificant reaction force of compression is reduced, which reduces thedurability of the second swash plate 51 and the second shoes 25B.

(2-8) As the rolling elements of the radial bearing 52A, the rollers 52c are used. The roller bearing that uses the rollers 52 c as the rollingelements has superior load bearing properties as compared to, forexample, a case where balls are used as the rolling elements. Thisreduces the size of the radial bearing 52A, which reduces the size ofthe compressor 10.

(2-9) The race 55 is located between the rollers 53 a of the thrustbearing 53 and the first swash plate 18. The race 55 is rotatablerelative to the first swash plate 18.

In a case of a configuration in which, for example, the rollers 53 a ofthe thrust bearing 53 roll directly on the first swash plate 18, asignificant reaction force of compression is concentrated on part of thefirst swash plate 18 (part of the first swash plate 18 corresponding tothe piston 23 located in the vicinity of the top dead center position),which may cause partial wear and deterioration. However, in the secondembodiment, since the race 55 is provided between the rollers 53 a andthe first swash plate 18, the reaction force of compression applied tothe rollers 53 a is applied to the first swash plate 18 with reducedcontact pressure via the race 55. Therefore, the first swash plate 18 issuppressed from being partially worn and deteriorated. Also, as for therace 55 that rotates relative to the first swash plate 18, the sectionto which a significant reaction force of compression is applied via therollers 53 a is sequentially changed. This prevents the race 55 frombeing partially worn and deteriorated.

(2-10) The engaging portion 18 d is provided on the outercircumferential portion 18-1 of the first swash plate 18 and extendstoward the second swash plate 51. The race 55 is engaged with the firstswash plate 18 by abutting against the engaging portion 18 d at theradially outward edge of the race 55.

For example, in a configuration in which the engaging portion isprovided at the inner circumferential portion of the first swash plate18 and the race 55 is engaged with the first swash plate 18 at theradially inward edge, when lubricant (refrigerant oil) that is adheredto the first swash plate 18 moves radially outward by centrifugal force,the engaging portion hinders the lubricant from entering between thefirst swash plate 18 and the race 55. However, the second embodiment inwhich the race 55 is engaged with the first swash plate 18 at theradially outward edge prevents the engaging portion 18 d from hinderingthe lubricant from entering between the first swash plate 18 and therace 55. Thus, the first swash plate 18 reliably slides with respect tothe race 55.

(2-11) The engaging portion 18 d has an annular shape. Therefore, theengaging portion 18 d is stably engaged with the race 55. Thus, the race55 further reliably slides with respect to the first swash plate 18.

Next, a third embodiment of the present invention will be described withreference to FIG. 5. In the third embodiment, only differences from thesecond embodiment are explained. Like or the same members are given thelike or the same numbers and detailed explanations are omitted.

In the third embodiment, the support portion 39 is not decentered fromthe axis M1 of the first swash plate 18. That is, the second swash plate51, the radial bearing 52A (see FIG. 3), and the thrust bearing 53(including the race 55) are not decentered from the first swash plate18. In this case, as for part of the outer circumferential edge of thefirst swash plate 18 that corresponds to the piston 23B located at thebottom dead center position, the salient corner 18 c need not bechamfered as shown in FIG. 5 because the salient corner 18 c toward thesecond swash plate 51 does not significantly project in the radialdirection from the second swash plate 51.

Furthermore, in the third embodiment, the PCD of the thrust bearing 53is greater than the diameter of an imaginary cylinder defined about theaxes M1, M2 of the first swash plate 18 and the second swash plate 51and passes through the center points P of the first shoe 25A and thesecond shoe 25B. In this manner, the thrust bearing 53 (the rollers 53a) receives the reaction force of compression transmitted through thesecond swash plate 51 in a suitable manner, which improves thedurability. The “PCD” of the thrust bearing 53 refers to the diameter ofan imaginary cylinder having the axis at the center of the thrustbearing 53 (at the axes M1, M2 of the first swash plate 18 and thesecond swash plate 51) and passes through the mid point of the rotatingaxis of the rollers 53 a.

Next, a fourth embodiment of the present invention will be describedwith reference to FIGS. 6 to 8. In the fourth embodiment, onlydifferences from the first and second embodiments are explained. Like orthe same members are given the like or the same numbers and detailedexplanations are omitted.

The rotor 17 is fixed to the drive shaft 16, and a swash plate 58 issupported on the drive shaft 16. The swash plate 58 is permitted toslide along and incline with respect to the drive shaft. Coupling pieces59, 60 are fixed to the swash plate 58, and guide pins 61, 62 are fixedto the coupling pieces 59, 60. A pair of guide holes 171 (only one isshown) is formed in the rotor 17. Head portions of the guide pins 61, 62are slidably fitted to the guide holes 171. The engagement of the guideholes 171 with the guide pins 61, 62 allows the swash plate 58 toincline with respect to the axial direction of the drive shaft 16 androtate integrally with the drive shaft 16. The inclination of the swashplate 58 is guided by the guide holes 171 and the guide pins 61, 62, andthe drive shaft 16. The coupling pieces 59, 60, the guide pins 61, 62,and the guide holes 171 form a hinge mechanism 19A.

The swash plate 58 shown by a solid line in FIG. 6 is in the maximuminclination state of the swash plate 58. When the center of the swashplate 58 moves toward the cylinder block 11, the inclination of theswash plate 58 decreases. The swash plate 58 shown by a chain line inFIG. 6 is in the minimum inclination state.

Part of the outer circumferential edge portion of the swash plate 58corresponding to the piston 23A located at the top dead center positionand circumferentially adjacent parts thereof are provided with aninclined surface on a salient corner 58 a opposite to the piston 23.That is, part of the outer circumferential edge portion of the swashplate 58 corresponding to the vicinity of the hinge mechanism 19A isprovided with the inclined surface on the salient corner 58 a toward thehinge mechanism 19A. In other words, part of the outer circumferentialedge portion of the swash plate 58 corresponding to a circumferentialrange of the swash plate 58 that arranges the piston 23A at the top deadcenter position is provided with the inclined surface on the salientcorner 58 a opposite to the piston 23. As shown in FIG. 7, part of theinclined surface of the salient corner 58 a corresponding to the piston23 located at the top dead center position is the largest, and graduallybecomes smaller along the circumferential direction.

As shown in FIG. 8, when the swash plate 58 is in the maximuminclination state, the inclined surface provided on the salient corner58 a is located on the circumferential surface of an imaginary cylinderC having an axis M3 that is parallel to the axis L of the drive shaft16. In the example shown in FIG. 8, the axis M3 is displaced withrespect to the axis L from the piston 23A located at the top dead centerposition toward the drive shaft 16. The diameter of the imaginarycylinder C is greater than or equal to the diameter of the swash plate58.

At the outer circumferential edge portion of the swash plate 58 thatcorresponds to the piston 23A located at the top dead center position,the salient corner 58 a opposite to the piston 23 significantly projectsin the radial direction of the drive shaft 16 when the swash plate 58tilts with respect to the drive shaft 16. Therefore, providing theinclined surface at the projecting portion (part of the salient corner58 a) of the swash plate 58 permits the swash plate 58 to be enlargedwhile suppressing reduction in the durability and enlargement of thepistons 23. Therefore, a significant reaction force of compressionapplied to the swash plate 58 is received in a suitable manner via thesecond shoe 25B of the piston 23 located in the vicinity of the top deadcenter position. This improves the durability of the swash plate 58.

It should be understood that the invention may be embodied in thefollowing forms without departing from the spirit or scope of theinvention.

(1) In the first embodiment, the radial bearing 52 may be omitted, andthe second swash plate 51 may slide with respect to the support portion39.

(2) In the first embodiment, the thrust bearing 53 may be omitted, andthe second swash plate 51 may directly slide with respect to the firstswash plate 18.

(3) In the first embodiment, the radial bearing 52 and the thrustbearing 53 may be omitted, and the second swash plate 51 may be securedto the first swash plate 18 so that the second swash plate 51 rotatesintegrally with the first swash plate 18.

In this case, part of the outer circumferential edge portion of thesecond swash plate 51 corresponding to the piston 23A located at the topdead center position is provided with an inclined surface (a chamfer) onthe salient corner toward the first swash plate 18. In addition, part ofthe outer circumferential edge portion of the second swash plate 51corresponding to the piston 23B located at the bottom dead centerposition is provided with an inclined surface (a chamfer) on the salientcorner opposite to the first swash plate 18.

With reference to FIG. 2, when the second swash plate 51 inclines withrespect to the drive shaft 16, the salient corner toward the first swashplate 18 significantly projects in the radial direction of the driveshaft 16 at the outer circumferential edge portion of the second swashplate 51 that corresponds to the piston 23A located at the top deadcenter position. Also, at the outer circumferential edge portion of thesecond swash plate 51 corresponding to the piston 23B located at thebottom dead center position, the salient corner opposite to the firstswash plate 18 significantly projects in the radial direction of thedrive shaft 16. Therefore, providing the inclined surfaces (thechamfers) at the projecting portions (part of the salient corners) ofthe second swash plate 51 permits the second swash plate 51 to beenlarged while suppressing reduction in the durability and enlargementof the pistons 23. Therefore, the contact area between the second shoe25B of the piston 23 located in the vicinity of the top dead centerposition and the second swash plate 51 can further be increased, whichfurther improves the durability of the second swash plate 51 and thesecond shoe 25B.

(4) In the first embodiment, two swash plates, which are the first swashplate 18 and the second swash plate 51, are used. However, for example,a third swash plate may be arranged between the second swash plate 51and the second shoes 25B. That is, the swash plate configuration towhich the present invention may be applied is not limited to the onethat uses the first swash plate and the second swash plate, but theswash plate configuration may include a number of swash plates such asthree, four, or five swash plates.

(5) The present invention may be applied to a variable displacementswash plate type compressor including double head pistons. In this case,the second swash plate may be arranged on either the front or rearsurfaces of the first swash plate, or may be arranged on each of thefront and rear surfaces of the first swash plate.

(6) The present invention need not be applied to the refrigerantcompressor of the refrigeration circuit, but may be applied to, forexample, an air-compressor.

(7) The second embodiment may be modified such that, for example, thesliding surface 25 b of each first shoe 25A is flat as shown in FIG. 5.

(8) The second embodiment may be modified such that, for example, thesliding surface 25 b of each second shoe 25B is dented at the center asshown in FIG. 5. In this case, the weight of each second shoe 25B, whichreciprocate with the associated piston 23, is reduced, which reduces theinertial force of the second shoe 25B. Therefore, the inclination angleof the first swash plate 18 and the second swash plate 51, that is, thedisplacement of the compressor is smoothly changed.

(9) In the second and third embodiments, the thrust bearing 53 may bechanged to a roller bearing, which includes balls as the rollingelements.

(10) In the second and third embodiments, the thrust bearing 53 may bechanged to a sliding bearing.

(11) In the second and third embodiments, the radial bearing 52A onlyreceives a radial load (a load perpendicular to the axis M2) applied tothe second swash plate 51. Instead, for example, the rollers 52 c may betilted with respect to the axis M2 of the second swash plate 51 suchthat the radial bearing 52A also receives a thrust load (a load alongthe axis M2) in addition to the radial load.

(12) In the second and third embodiments, the thrust bearing 53 onlyreceives the thrust load applied to the second swash plate 51. Instead,for example, the rollers 53 a may be tilted with respect to the surfaceof the second swash plate 51 such that the thrust bearing 53 alsoreceives the radial load in addition to the thrust load.

(13) In the second and third embodiments, the race 55 may be omitted,and the rollers 53 a of the thrust bearing 53 may roll directly on thefirst swash plate 18.

(14) In the second and third embodiments, the engaging portion 18 d maybe omitted, and an engaging portion may be provided on the innercircumferential portion of the first swash plate 18 (for example, theproximal portion of the support portion 39 may serve also as theengaging portion) so that the race 55 is engaged with the first swashplate 18 on at radially inward edge.

1. A variable displacement swash plate type compressor, comprising adrive shaft, a swash plate coupled to the drive shaft to be rotatableintegrally with the drive shaft, pistons coupled to the swash plate viashoes, rotation of the drive shaft rotates the swash plate, which causesthe pistons to reciprocate and compress gas, and the displacement ischanged by varying the inclination angle of the swash plate, and aninclined surface provided at part of the entire outer circumferentialedge portion of the swash plate.
 2. The compressor according to claim 1,wherein part of the outer circumferential edge portion of the swashplate corresponding to the piston located at the top dead centerposition is provided with the inclined surface on a salient corneropposite to the piston.
 3. The compressor according to claim 1, whereinpart of the outer circumferential edge portion of the swash platecorresponding to the piston located at the bottom dead center positionis provided with the inclined surface on a salient corner toward thepiston.
 4. The compressor according to claim 1, wherein the swash plateincludes a first swash plate, which is coupled to the drive shaft to berotatable integrally with the drive shaft, and a second swash platesupported by the first swash plate, the pistons are coupled to the firstand second swash plates via first shoes, which abut against the firstswash plate, and second shoes, which abut against the second swash plateand receive a reaction force of compression, and part of the outercircumferential edge of the first swash plate corresponding to thepiston located at the top dead center position is provided with theinclined surface on a salient corner opposite to the second swash plate.5. The compressor according to claim 4, wherein part of the outercircumferential edge portion of the first swash plate corresponding tothe piston located at the bottom dead center position is provided withthe inclined surface on a salient corner toward the second swash plate.6. The compressor according to claim 1, wherein the gas is refrigerantused in a refrigeration circuit, and carbon dioxide is used as therefrigerant.
 7. A variable displacement swash plate type compressor,comprising a drive shaft, a swash plate coupled to the drive shaft to berotatable integrally with the drive shaft, pistons coupled to the swashplate via shoes, rotation of the drive shaft rotates the swash plate,which causes the pistons to reciprocate and compress gas, and thedisplacement is changed by varying the inclination angle of the swashplate, a first inclined surface provided at part of the outercircumferential edge portion of the swash plate corresponding to thepiston located at the top dead center position on a salient corneropposite to the piston, and a second inclined surface provided at partof the outer circumferential edge portion of the swash platecorresponding to the piston located at the bottom dead center positionon a salient corner toward the piston.